<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta http-equiv="X-UA-Compatible" content="IE=edge" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Document</title>
  </head>
  <body>
    <div id="app">
      <button>改变文本</button>
    </div>
    <!-- 注意: 部署时，将 "development.js" 替换为 "production.min.js"。-->
    <!-- jsx特点：多个标签最外层（根）只能有一个标签 -->
    <script
      src="https://unpkg.com/react@16/umd/react.development.js"
      crossorigin
    ></script>
    <script
      src="https://unpkg.com/react-dom@16/umd/react-dom.development.js"
      crossorigin
    ></script>
    <script src="https://unpkg.com/babel-standalone@6/babel.min.js"></script>

    <script type="text/babel">
      // 封装APP组件
      class App extends React.Component {
        constructor() {
          super()
          // this.message='Hello World'
          this.state = {
            message :"Hello World"
          } 
        }
        render() {
          return (
            <div>
             <h2>{this.state.message}</h2>
             <button onClick={this.btnClick.bind(this)}>改变文本</button>
            </div>
          )
        }
        btnClick() {
          // console.log('按钮发生了点击',this.state.message);
          // this.state.message = "Hello React"
          this.setState({
            message:"Hello React"
          })
        }
      }
      // 渲染组件
        ReactDOM.render(
          <App/>,
          document.getElementById("app")
        );
    </script>
  </body>
</html>
